


Lessons in Applied Physics

by preussisch_blau



Series: Blame It on the River [2]
Category: The Flash (TV 2014)
Genre: Biochemistry, Fist Fights, Gen, Gratuitous use of movie quotes, Harry is a dick, Physics, Possibly Pre-Slash, Potentially Inaccurate Science, but we knew that already, complicated feelings
Language: English
Status: In-Progress
Published: 2016-01-06
Updated: 2016-01-13
Packaged: 2018-05-12 05:27:31
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 13,486
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5654125
Author URL: https://archiveofourown.org/users/preussisch_blau/pseuds/preussisch_blau
Summary: <blockquote class="userstuff">
              <p>"Fight me."</p><p>"I- what?!" The look Harrison got was almost adorably confused.</p><p>…No, it was just confused, there was nothing cute or endearing about it.</p><p>"I'm a bit restless. You could use the practise. So. Fight me," he explained.</p><p>(Or, the present life of Harrison Wells, as framed by science.)</p>
            </blockquote>





	1. Newton's Second Law

**Author's Note:**

> Follows These Are the Shadows, but you don't need to read that one first at all.
> 
> Entirely inspired by that one pic where Tom and Grant are just flopped against the wall in their suits. Somehow my mind went to Harry instead of Eobard, though.
> 
> Lemme know if I messed up any canon details. I reviewed the stuff I wasn't sure of, but it is not without the realm of possibility that I missed something.

He was restless. Which made perfect sense, considering what he had agreed to just last night. Still, he would have thought that the late night, the fitful sleep he'd barely gotten, would have made him too exhausted to want to do much of anything today.

Instead, Harrison felt like he was about to climb out of his skin. The sort of jittery, crawling sensation that he hadn't felt this intensely since he was young and less experienced and had thought that he could survive his final year working on his master's thesis by coffee alone. He paced back and forth for a few moments, pondered whether a run would help burn off this awful, anxious energy.

No, he decided, it wouldn't help at all. He knew himself well enough to know that this was the result of feeling helpless, which meant he needed to do something that felt _productive._ And running had never felt productive to him. Meditative, yes. But the last thing he really wanted to do was be stuck in his own head again.

Harrison made his way to the Cortex. As he walked, he considered his options. With the clarity of day, he noted there was nothing saying that his end goal _had_ to be to assist Zoom. Considering the nature of their deal was that he made Barry _stronger_ , there was the possibility to -somehow- double-cross the speed demon. Not that the idea was perfectly appealing with Jesse still in his clutches, but at the same time…

The idea of betraying Barry didn't sit well with him either.

He wasn't that kind of man, the kind of man who'd lie to someone's face about his intentions for them. Who would build them up, earn their respect, solely for his own selfish gain. Which might have shocked certain people, because goodness knew he had absolutely no problems with manipulating public perception. He knew how to play the media like a fiddle, had the citizens of Central City practically eating out of his hand. But that was different. They weren't anyone he knew, anyone he cared about beyond needing them to stay out of his way.

He'd made it clear from day one that he needed help from the Flash and his friends to stop Zoom, and if he hadn't mentioned that it had become personal for him… Well, it was a difficult thing, baring one's soul. Especially when the people you might have revealed yourself to were convinced you were everything they hated and feared. But he hadn't _lied_ about why he wanted their help.

The chair he chose creaked as he settled down into it. Harrison stared at the monitor in front of him, but didn't reach to turn on the computer just then. Instead, he watched himself, dimly reflected by the black screen. Was there anything in his face that would give him away? Because he couldn't have the others find out, not yet. Not until he knew how to tell them without Zoom knowing he'd done so. Not until he was certain he could truly double-cross the bastard.

A blink of yellow sparks was reflected in the screen, so he spun the chair around to face Barry.

"Well, this is a surprise," he remarked, one eyebrow raised just slightly above the other. "What brings you here? It's Christmas."

Barry looked hesitant, nervous, but he shrugged and smiled nonetheless. Harrison wasn't convinced he deserved that smile.

"Yeah, I know. Just… Wanted to see how you were doing." He paused, then looked pained. "Sorry, that was stupid, wasn't it?"

He couldn't help the soft laugh that escaped him, even though it felt wrong in his throat. "Possibly."

Barry shifted his weight, back and forth, back and forth. The motion should have annoyed him, he wasn't overly fond of fidgeting, but it appeared he'd reached system overload on frustration and his mind had just shut all that down. All he really felt was that itching energy under his skin, and the lingering promise of exhaustion.

He decided to break the silence then, before Barry decided he had better places to be, because he had a growing idea on how to work off some of his tension and he needed some help for that. "I don't suppose you have some time to do me a favor?"

"Yeah, sure," Barry tilted his head as he spoke and finally stilled. "What is it? I've got all day. Well. Not all day all day, because I'm sure Joe and Iris will want to see me again at some point but-"

Harrison cut Barry off by holding up his hand. "Understood. It shouldn't take more than a couple hours out of your morning."

Barry nodded. "Alright. So, what is it?"

"Fight me."

"I- what?!" The look he got was almost adorably confused.

…No, it was just confused, there was nothing cute or endearing about it.

"I'm a bit restless. You could use the practise. So. Fight me," he explained. Harrison folded his hands together in his lap and rested his head back against the chair.

"Um, you know I train with the Green Arrow, right? I'm not sure that's a good idea."

"Ah, yes, I forgot that's why you run off to Star City every night." There was nothing in his tone that wasn't sarcastic, but there was also nothing biting about it. He meant less to be mean and more to tease him a little.

"…Okay, so it's been a while," Barry muttered. He crossed his arms over his chest and looked down at the ground pensively, then back up. "I'm guessing the first rule is I can't use my speed?"

"Considering I'd prefer my bones remain unbroken, yes. That would be the first rule."

"Hey, I've never broken anyone's bones," Barry frowned.

That made both of Harrison's eyebrows shoot up. "Then you _really_ need practise."

He stood and motioned for Barry to follow him down to the parking garage, where there would be plenty of room for them to spar. That didn't mean he missed the incredulous look he got, or the faint squawk of something that was either shock or indignance.

"What? What does _that_ have to do with anything?"

As he passed Barry, the younger man turned and joined him. "Force equals mass times acceleration, Barry. It takes at least 4 000 newtons of force to fracture a femur. A professional fighter can deliver a punch with 5 000 newtons behind it. _You_ could _tap_ someone with almost 1 000 newtons. There is absolutely no reason that you should _not_ have broken someone's bones by this point, unless you are either deliberately pulling your punches or have no idea _how_ to punch."

He came to a halt as he finished his point, turned to give Barry a sharp look as he evaluated him, considered which of the two scenarios he had posited was more likely. Hopefully the former, otherwise he was going to have words with Mr Queen. Not that he couldn't fix both problems, but what was the point in training someone if you didn't train them properly?

"Oh," Barry managed after a moment of being stared at. "I… okay. You have a point there."

"Mm. So which is it?"

"Sorry?"

He sighed, shoved his hands in his pockets because they weren't sparring _yet_ and the urge to smack Barry for not being as intelligent as he knew the boy was was strong. "Are you pulling your punches or do you not know how to fight?"

"…I… uh…"

"And you said you were being trained," he remarked drily.

"Well… it was only a couple of sessions? I've kinda had to figure out most of the fighting stuff by myself," he confessed.

"Mm." That explained a great deal, like why Barry tended to return from fights more beat up than any man who could outrun the overwhelming majority of his opponents had a right to. Harrison thought for a moment. His gaze slipped from Barry's face to the wall as he considered what he would do. Not knowing how to fight was an easy fix. If Barry was unconsciously pulling his punches, which wouldn't surprise him given Barry's personality… he had an idea how to work on that as well. Though he wasn't fond of it. And doubted Barry would like it either.

Unfortunately, he was fairly certain after the hesitance Barry had displayed when he asked him to fight, that it would take a rather extreme measure to get the boy to actually _hit_ him.

Well, nothing for it.

"Will you actually try to hit me, or will I be wasting my time?" Harrison asked.

Barry frowned in a way that made him look far too much like a kicked puppy for Harrison's personal comfort. "I don't want to hurt you. I mean, you got _shot_ a few weeks ago."

He resisted the almost overwhelming urge to sigh. "Would it help if I wore the suit?"

"What?!"

"Would you actually _try to hit me_ if I wore _that damn yellow suit._ " He wasn't sure how he could make this any clearer.

Barry was looking at him like he'd absolutely lost his mind. Honestly, he was wondering the same thing himself.

"You. Want me. To actually try to hurt you." Barry said slowly, as though he wasn't quite sure he was hearing Harrison properly. "And you're willing. To dress up like him. To get me to do that."

"Well, it does sound a bit odd when you put it like that," he replied with forced lightness, "But truthfully, if your problem is form, that can be fixed very easily. If your problem is you're not trying to hurt your opponent… Well, that can't be fixed unless I can get you to actually _want_ to hit your opponent."

He was still getting a skeptical look, but he also saw the gears turning in Barry's mind as he mulled those words over.

Hopefully Barry didn't get the wrong impression. It was less that he wanted to be hurt -there were many things he enjoyed, but pain was not on that list-, and more that he needed an actual _fight._ There was no enjoyment to be had in just beating up someone he cared about. If he wanted a human punching bag, he was certain that if he waited until evening he'd be able to find a seedy bar filled with belligerent drunks _somewhere._

But there wasn't much challenge in that.

"And what are you getting out of this deal again?" The question was suspicious.

"I," he said, tone deceptively soft, "get some exercise."

"Exercise. Riiiight."

He was definitely going to nip that wrong impression in the bud _now._

He understood Barry's skepticism, really he did, but it was a little grating. He exhaled slowly through barely open lips. He debated with himself for a moment, but in the end, he really didn't enjoy lying to people he actually _liked._ Those kind of people were few and far between for him, and he knew well enough that lies could easily alienate them. Add in the inherent mistrust in this situation because of a man who had stolen his face, and… complete honesty, as much as the thought left a sour taste in his mouth, was the best policy here if he wanted compliance.

"The truth is…" Harrison finally looked back at Barry, made sure he met his eyes, "I'm feeling a bit. Helpless. I've spent the better part of the night stuck in my own head, trying to think of a way out of this situation and failing miserably. If we spar, I'll be focusing on sparring. If you're not willing to give me a real fight, that's fine, I won't be upset. But I would appreciate the chance to let off some steam. And I would feel guilty if I went into this intending to actually hit you, but you didn't have the same intentions."

As he spoke, he saw the light of understanding dawn in Barry's eyes. Until finally, Barry blinked, nodded slowly once, and then again in a quick, decisive motion. Then he turned back towards the Cortex, which left Harrison momentarily confused, until Barry looked over his shoulder with a grin.

"If this is supposed to help me fight as the Flash, I should probably get my suit as well," he said.

That… was actually a rather good idea. He should have thought of it first. "As well?" he asked.

"We-ell… It might be a good idea if you wore yours. Er. His. Not 'cause I need incentive to hit you, but," Barry canted his head slightly, lips twisted in thought, "if we're gonna go all out, having some padding might be good."

His jaw tightened involuntarily when Barry called the Reverse Flash's costume his, but he let the slip go. If only because he really was just done with emotions for the time being, and dwelling on it served him no good. "A valid point. I'll meet you in the parking garage?"

"…Sure. Be there in a flash!" Barry winked -he _winked!_ \- and darted off to the Cortex, lightning crackling in his wake.

Harrison ran his hand through his hair as he watched the energy fade, then shook his head and turned to go find that damn suit.

* * *

He wasn't at all surprised to see Barry sitting on the hood of one of the vans, waiting for him, when he pushed the door open. After all, the no speed rule wasn't in effect yet. He quirked an eyebrow when he noted that Barry's cowl was still down behind his neck. "Good thing I didn't say we'd be starting as soon as I got here."

Barry looked at him, and it made Harrison's skin crawl in an unsettling counterpoint to his pre-existing nerves. He felt almost like a subject under a microscope, though he wasn't sure if he was reading too much into Barry's gaze or not. He crossed his arms over his chest and decided to just wait it out.

Then Barry grinned widely. "Wow."

"What?" he snapped, and immediately regretted it, because nothing mean had been said or done.

"Nothing. I'll tell you later." Barry hopped down off the van and moved out into the empty expanse of the garage. "So, no speed. Any other rules?"

He followed Barry with his eyes until the young man stopped. Then he made his way over, steps carefully light, until he was well within arm's reach. "Let's try to avoid hits above the collar. Neither of us needs a concussion."

"What about below the belt?" Barry joked.

Harrison pretended to give it careful consideration before responding with a perfectly flat, "I already have a child, so it doesn't matter to me."

The way Barry turned about as red as his suit, sputtered between being horrified, amused, mortified… _Well._

"That's. You. Wh. Harry!"

"Hm?"

"That's awful!"

He smiled slightly, just the corner of his mouth. "I know."

Barry shook his head, the shocked expression not quite leaving his face. "Oh man… What am I gonna do with you?"

"Well. Now that we have the rules established… you could hit me?" He held his hands apart in invitation.

"I could… but first." Barry tugged his cowl into place.

After a moment, Harrison decided that he probably ought to do the same. Even if they weren't supposed to aim for the head, putting some protection in place wasn't a bad idea. Though it made things a little more difficult for him, decreased the range of motion in his neck from what he was used to.

"Now are we ready?" he asked.

Barry nodded.

"Then… begin."

He slid his right foot out to the side and back. Brought his hands up, loosely cupped, in front of his chin, but well out of his field of vision. Watched as Barry widened his legs a bit and held up tight fists. Swung wide, too wide, he'd be off balance at the full extension of his arm. Perfect. He twisted, turned towards Barry's fist as it approached, grabbed hold of his arm, and helped him along.

Barry hit the floor on his side when Harrison let go. He looked a bit dazed. Harrison aimed a kick at his stomach, but Barry rolled out of the way, pushed up to his feet. And, he had to give him credit, tried again. This time with a slight running start to bring him back into range.

This time, he brought up his arm to block, shove Barry's fist aside. Aimed his own fist for Barry's side and drove it in hard. Barry wheezed when his fist connected. Harrison stepped away quickly, brought his hands back up in a guard, and grinned.

"Stop trying to hit me and hit me," he teased.

"Are you _sure_ I can't use my speed?" Barry asked with a high-pitched laugh. He rubbed at his side for a moment, though he definitely kept his eyes on Harrison. Good. He at least knew not to let his guard down entirely.

"Positive. Now, come on." He made a beckoning motion with the fingers of his right hand.

"Ughhh," he groaned, but Barry moved closer anyways, fists raised once more.

Harrison took the opportunity to drop down and kick Barry's legs out from underneath of him.

The combination of 'smack' and "Ow!" was somewhat satisfying, but Barry sorely needed help. He dropped his guard and stood straight, looked down at Barry from his full height.

"Up," he said.

"You're gonna hit me again, aren't you?"

"Well, your enemies won't stop just because you've taken a few blows."

Barry thumped his head lightly against the pavement. "You may be right, but you're still an asshole, you know that?"

"If you get up, I'll tell you what you're doing wrong." He was not above bribery, after all. It was just very rarely the most efficient or effective way to get things done. As an afterthought, he added, "And I won't hit you for two minutes."

"That's not very long…" Despite the complaint, though, his words seemed to work, because Barry sat up, then pushed himself to his feet, albeit warily.

Harrison nodded at him, then took up his guard again. Barry's eyes widened, but before he could say anything about what Harrison had _just_ said, Harrison interjected. "I'm not going to hit you. Do me a favour, and take your stance."

Barry shut his mouth, brought his fists up in front of his face and shifted his legs apart to just past shoulder width. It wasn't _terrible,_ because it was a lot more than most amateurs he'd seen would do, but it spoke more of someone who had been trained in passing, given the basics a long time ago and never really forced to practise them.

"Move your right leg back, and bring it a little closer in. Make sure you stay evenly balanced."

He half-expected questions, possibly an argument. But Barry complied readily. Which brought a warm feeling to his chest, oddly enough. He didn't care to examine that sensation too closely, though, so he pushed it away.

"Good. Now, hands down to your chin, and unclench your fists."

That was where he got the question, which didn't surprise him.

"Okay, question. If the point is that I'm preparing to hit you, why shouldn't I have my hands in fists?" Barry's eyebrows were hidden by the mask, but the wrinkles that formed around his eyes were a clear enough indicator that he was furrowing them.

"Fighting isn't just _punching._ You didn't hit the ground the first time because I punched you; you hit the ground because I _threw_ you. You should be ready to do anything. Grab your opponent, hit them, block them." Harrison curled his fingers further, then relaxed them. "Among other reasons. Now. Hit me, as hard as you can with your right hand, _without_ using your speed."

Barry nodded at him, then clenched his right fist and swung. Harrison opened his guard and let it connect with his chest, a dull thump. He was suddenly grateful for the padding, because that might have actually hurt otherwise.

"Not bad. You're swinging too wide, though. Keep your arm in line with your body. And rotate from your feet as well, not just your hips and shoulders."

"…Why does that sound familiar?" Barry muttered.

Harrison stared blandly at him. "Possibly because your Green Arrow has told you this before, if you've actually trained with him."

"…Shut up."

"Again."

Barry huffed and tried again, and Harrison let him connect again. It was definitely a stronger blow, but there were still the same flaws in his form. Harrison shook himself slightly, then adjusted his stance a bit.

"I'm going to demonstrate."

"It has not been two minutes."

"I'd say 'fight me, Barry', but I'd rather you _not_ fight me on this one," he remarked. "Now, guard, but don't block."

That earned him another groan, which he ignored. But Barry obeyed, kept his stance up the way he'd been told. Harrison took a deep breath, then snapped his hand forwards, made a fist as he moved. He turned into the punch, pushed off from his right foot with enough force his heel left the floor, and struck, knuckles colliding with Barry's chest.

Barry stumbled backwards a couple of steps. Coughed. "Whoa. Okay. That actually hurt."

"Mm. Did you see what I did?"

"Uh. Yeah? I think so."

"Then get back over here and try to copy it."

* * *

Sweat ran down his face, his blood sang in his ears, and he was quite possibly a walking bruise by this point, but Harrison couldn't say he hadn't had fun. Either Barry was a quick learner, or he'd been holding back a bit until he'd seen that Harrison definitely knew what he was doing, but that didn't matter. He'd ceased instruction some time ago, and they had moved on to actual fighting.

It was interesting, he noted when they finally took a break, actually seeing how Barry fought. Even at a normal speed, there was still a certain swiftness to his strikes. He favoured getting in his hits in rapid succession, then backing off to go in again from a different angle. With a bit more practise on his precision, Harrison was fairly certain he could be quite devastating, so he hadn't bothered too much on trying to get Barry to hit _harder_ once he'd figured out his style. Instead he'd shifted his focus to aim.

Which had actually posed an interesting challenge for himself, considering he had always favoured hard, brutal strikes that would take someone down in as few moves as possible. He'd found that precise aim wasn't necessarily as important, because he rarely went for the smaller targets like the throat or smaller bones and joints. He preferred the torso, the head -though he avoided Barry's today because of the rules-, the legs.

But Barry. With his speed, if he had surgical precision… Oh, he could easily take almost anyone down, and not even worry overmuch about force.

He rested his head back against the wall and just breathed for a moment. There was a light thump against his shoulder, so he opened one eye to glance downwards. Ah. Barry's head. He closed his eye again and smiled.

"I'm done." The words carried an almost plaintive tone that made Harrison chuckle in response.

"Yes," he agreed. He wasn't entirely certain if he'd be able to stand back up any time soon. Every muscle in his body felt like a lead weight that pinned him to the ground. Though those were good aches, not like the one in his chest that throbbed with every heartbeat. Perhaps this hadn't been the best idea, not when he was still recovering from being shot, but he wasn't about to let Barry know that.

"Oh thank _God,_ " Barry breathed. "I was beginning to think you weren't actually human."

That made him proverbially sit up. Proverbially, because he was hardly inclined to attempt moving from his somewhat sprawled position, regardless of the fact that he was at present being used as a pillow. "Oh?"

"You're like… I dunno. A Terminator or something. You hit _hard_ for. Uh…" Barry trailed off, like he wasn't quite sure finishing that sentence was the wisest idea.

"For an old man?" Harrison suggested.

"You said it, not me."

He exhaled the smallest of chuckles.

They sat in silence for another few moments, until Barry spoke again. "Where'd you learn to fight like that, anyways?"

He mulled the question over in his head, not so much deciding how to answer as how _much_ to answer. "I was… not entirely popular as a child. My father taught me how to fight after I came home from school one day with a black eye. Beyond that… practise. I'm told I am remarkably good at pissing people off."

Barry snorted, shifted against him. "Joe taught me and Iris how to box. She was better at it, though."

"If that is still the case, then remind me to never get on her bad side," he muttered.

Which earned him a genuine laugh, short and slightly breathless as it was. "I'm not that good."

"The fact that my bruises have bruises would beg to differ."

He felt another shift that led to Barry's elbow digging uncomfortably into his ribs and fingers pressed awkwardly against his thigh and the loss of weight on his shoulder. Harrison looked down, eyes opened to narrow slits, to see that Barry had turned to look up at him, concern written on his face. "I didn't hurt you too badly, did I? …Oh shit, you're still _healing._ Caitlin's gonna kill me…"

" _Barry,_ " he sighed, "Ignoring the fact that I am a grown man capable of making my own decisions about my health; my chest feels _fine._ You have not aggravated anything. Now. Settle down."

He brought his hand up behind Barry's back and twined his fingers into his hair, then gently tugged him back towards where he'd been laying seconds before. The lie tasted like metal in his mouth -or perhaps that was just the inevitable slight dehydration speaking-, but he was fairly certain if he admitted to being in pain from the bullet wound, Barry would not agree to anything like this ever again.

Barry scowled at him, and it was the most petulant expression he had ever seen on a grown man's face, but allowed himself to be moved back into place. He squirmed a bit against Harrison's chest, until he finally settled in a position that, mercifully, did not cause any of his bones to press painfully against him, nor involved Barry's hand lingering on him any longer.

He was going to remove his own hand.

Eventually.

"You know, I wasn't all that popular as a kid either. Between being a total nerd, and the whole Dad being convicted of murder thing… I got beat up a lot. Though, I was told it was okay to run if I couldn't win," Barry rambled.

His mind was delightfully clouded with endorphins, which was why he allowed himself to rub the tips of his fingers in what was hopefully a soothing motion against Barry's scalp. At least, that was what he told himself. In some regards, Barry reminded him painfully of himself. Or what he could have been, if he had been more hopefully idealistic and less pragmatically creative. "You can't always run from a losing battle."

"Trust me, I've figured that one out for myself." He felt more than heard the humourless laugh that accompanied that statement. "Though, gotta admit, I'm pretty bad sometimes about not giving up on hopeless things."

Harrison drummed his fingers lightly before he remembered it was Barry's head that he was using as a percussion piece. "I understand. My master's thesis was on neutrino oscillation. I was convinced it actually occurred. There just wasn't any evidence to support my hypothesis."

"Huh. They proved that one in, uh, 1998, I think?"

"So late?" he mused lightly.

"…Late?" Barry's head tilted under his hand, but otherwise didn't try to move to look at Harrison.

"I proved it in 1985."

"…You're shitting me."

"No. Is it wrong I'm still slightly bitter they didn't just hand me my doctorate while they were at it?"

He got a considering hum in response. "Depends. Did you earn a Nobel Prize for it?"

"Not for another twenty years," he shrugged.

"…No, yeah, go ahead and be bitter. I bet they were kicking themselves when that was announced. Like, oh, Harrison Wells just got a Nobel Prize for work he did as a _grad student_ and we couldn't even get over ourselves enough to give him his doctoral degree." Barry shifted his voice on the last sentence, took on an almost snooty accent that made Harrison grin hard enough his face hurt.

"At least _someone_ appreciates my work," he quipped.

Barry tensed against him, and he wondered if he said something wrong.

"…So, is there a biography about you on Earth-2?" was the question that revealed the source of Barry's tension.

"God, no," Harrison breathed. The mere idea… he shuddered. If there was ever to be any sort of book about his life, he fully intended to write it himself.

"Damn." And Barry actually sounded legitimately disappointed by that. "You know. Or, actually, you don't, but I'm gonna tell you. I read the other Dr Wells' biography _twice._ And that's just complete read-throughs. Can't tell you how many times I'd just re-read certain passages. And now… I dunno. I kinda was hoping I'd be able to read about the real deal."

The tension that had twisted in his gut and travelled up his spine at the mention of his false counterpart swiftly unravelled when Barry finished speaking. "If I ever allow such a thing to exist, I'll ensure you get a copy. I will even sign it, if you so desire."

Whatever Barry would have said in response was interrupted by an inordinately loud rumble from the younger man's stomach. He felt the flinch and heard the following chuckle.

"But first, I think, breakfast." He finally removed his hand from Barry's head and gently pushed him away. "Up."

Barry pulled away and clambered to his feet, then offered Harrison his hand. He took it without a moment's hesitation and pulled himself up as well. Standing was… well, perhaps it really had been sitting against the wall that had been bad, because he'd stiffened up a bit. Should have stretched some. Oh well.

"So… energy bar for me, definitely. Dunno what we've got here for you, though. Unless you've done some grocery shopping," Barry said as he withdrew his hand.

Harrison winced. "Ah, unfortunately, not recently. If you don't mind running to get me something when you're done…? Or, you could just share your energy bars. I'm sure I can fit the extra 7 000 calories into my diet _somewhere._ "

"…27 000."

"…Sorry, what?" Harrison shot him an incredulous look.

"They're about 30 000 calories each," Barry explained. "Not 10 000. So I could theoretically eat one for every meal -not that I'd ever _want_ to- and not have to eat anything else to meet my nutritional needs."

He thought about that. Calculated just how much Barry must eat otherwise if he wasn't eating those protein bars for every meal. Calculated his food costs. Shuddered. Banished those thoughts from his mind and instead wondered if not eating for the next… two weeks… Never mind.

"…You're getting me a McGriddle." He paused. "They _do_ have those on this Earth, yes?"

* * *

They entered the Cortex in companionable silence, to find Cisco and Caitlin seated at the computers, the lights in the room drastically dimmed. Caitlin had ridiculously large sunglasses on, whilst Cisco's head was pillowed on his forearms as he laid against the table. A faint groan escaped the boy, though he seemed otherwise unaware of their entrance.

"Hi Barry. Hi Harrison," Caitlin said in a strained tone, barely above a whisper.

"…Dare I ask…?" he raised an eyebrow at the duo, as he went to set his borrowed jacket and cowl down at an empty workstation.

"Shhh!" Cisco hissed, without the slightest movement of his head.

"I warned you guys how many times about the eggnog?" Barry asked incredulously. "And you two still drank that much?"

A pained whimper emanated from Cisco. "It was tasty…"

"It… didn't taste that strong this year…" Caitlin leaned forwards and rested her elbows on the desk, then her face in her hands.

Harrison was suddenly rather glad he'd decided to skip the party. Anything that led to this level of hangover tended to cause a level of drunken revelry he had no interest in being a part of prior. That, and if it didn't taste as strong as it was… He had his pride, and no interest in inadvertently getting fall-down drunk on _eggnog._

Barry sighed. "Well, I'm going to get Harry some breakfast. Need me to bring you guys coffee?"

"I love you? I love you forever?" Cisco replied, "By which I mean, oh Hell yes bring that sweet sweet caffeine."

"Please?" was all Caitlin had to say on the matter. "It should help while we wait for the aspirin to kick in."

After Barry left, a whirlwind of golden electricty, Harrison snorted. "You two came all the way here for aspirin."

"The world is quiet here," Cisco mumbled. "Also Caitlin wanted to check on how you were healing."

"Ah," he said, suddenly grateful for the dimmed lights and the fact that Caitlin was wearing sunglasses despite the darkness. She was probably going to have a fit when she saw how bruised he was. He turned away from the pair, then, and pressed the power button on the monitor in front of him. He adjusted the brightness of the screen down until it was only just visible. And then squinted, before deciding to just go and get his damn glasses, no matter how much his thighs protested the idea.

Unfortunately, he'd left them over by the computer where Cisco now sat. He sighed, and headed over, reminding himself that the movement would only help the soreness later, even if it hurt now. He stopped in front of the desk and reached over to grab his glasses. Which was when Cisco looked up, no doubt alerted to his presence by the further shade he cast over him.

Cisco blinked, frowned, and then pushed himself back from the desk at a rather impressive speed for someone not gifted with Barry's powers. He looked borderline scared to death for a moment, hand clutched over his chest in a defensive gesture. Harrison almost returned the frown… and then he remembered he was still wearing the rest of the suit, and even if he'd shed the jacket, the belt and pants were still fairly distinctive.

"The fuck?! Why are you wearing that?!" Cisco yelled, cringed, because he'd clearly made his headache worse for the moment.

Caitlin jolted in her seat with a whimper at the shout, and turned her head to look at Harrison. He couldn't make out her eyes at all, but the set of her face changed from something open and startled, to a distinct frown. "…Good question."

He unfolded his glasses and set them on his face, a sigh escaping despite his best efforts. "Barry and I were working on something, and we felt the extra padding offered by this suit would be beneficial."

"You could have gotten changed!" Cisco griped, still coming down from that jolt of fear.

"I could have," he agreed. The thought hadn't occurred to him, oddly enough, despite the fact that even on their way up from the parking garage Barry had occasionally been shooting him inscrutable glances. He'd been a little preoccupied, however, with the thought of food.

"What were you working o- Oh my _God,_ " Caitlin tugged her sunglasses down and grabbed his arm to pull it closer for a better look. "You're supposed to be resting! Not going out and getting beaten up while pretending to be someone else!"

"I was _not_ pretending to be anyone, and I'd _say_ you should see the other guy, but he's probably in better shape by this point." Harrison yanked his arm out of her grasp and folded it over his other arm to try to keep her from investigating further.

When Barry returned ten long minutes later, the lights in the Cortex were back to full brightness and Cisco had retreated to somewhere darker and quieter. Harrison had not allowed himself to be bullied into a bed, but he hadn't escaped Caitlin's concern entirely, if the fact that she was ranting about how she did not call Jay for help and subsequently stitch him back together for him to go and get into fights not even a month later when he knew he should still be taking it easy… Well, if any of that meant anything, at least.

Harrison spotted him and took the opportunity to slip out of the chair he'd been unceremoniously pushed down onto earlier. He snatched the offered bag from Barry's hand. " _Thank_ you," he muttered. Whether it was for the food or the distraction was not something he made clear. He set the bag on the nearest desk so he could rummage through it.

He, annoyingly, actually felt guilty for drawing Caitlin's attention to Barry, because she set in on him about how he could not just ask a man recovering from a gunshot wound to do whatever it was they had been doing that ended up with someone using Harrison as a punching bag.

He shouldn't have worried too much.

"Wait, wait, wait, _he_ was not the punching bag in this situation. _I_ was the punching bag," Barry defended himself with hands up in a placating gesture, the coffees having been set down at some point when Harrison wasn't looking. "Seriously, I still have bruises, and you _know_ how fast I heal."

"You were not a punching bag. Punching bags don't _dodge,_ " Harrison remarked casually around a mouthful of hashbrown.

Caitlin was far from stupid, so he's not surprised that, even with a hangover, she put two and two together and reached the correct conclusion as she looked back and forth between Barry and him. "You two were fighting each other?!"

Barry looked like he was about to bolt. Which, no. Hell no. Harrison casually reached over and grabbed Barry's wrist, just in time to feel a slight tug as the kid started, then stopped because he was being held.

"What, no, I'm leaving, this is _your_ fault and you are the one who deserves to be lectured," Barry babbled.

Harrison raised an eyebrow at him. "I in no way forced you into anything, so I would say the blame should be equally split."

"But you… you…" he sputtered.

"Made a request and gave the reason for it. That's all. Now. If I have to be lectured about my health, despite being an adult," he glared mildly at Caitlin as he said that, "then you can do the mature thing and listen as well since this _is_ , and I will be kind here, approximately forty percent your fault."

"…Forty percent?" Caitlin asked in a mild tone that Harrison didn't quite trust. There was definitely the edge of how was Barry less to blame if it was a simple case of request and agreement.

Harrison shrugged one shoulder. "He's the one who thought of the suit, without which I imagine I would be considerably more injured. So, forty percent."

"Really?" Caitlin asked, "Because the way I see it, he's entirely responsible since he _didn't have to agree to fight you._ "

She turned her attention to Barry, then. "You knew he was injured. You knew I had to perform surgery to keep him from bleeding out, and you fought him anyways! Not just that, but hard enough that he's got bruises on his arms and if I could get him to take off that tank top I'm sure I'd see more on his _chest-_ "

Barry glanced over at him as Caitlin continued, gave him a long-suffering look. "I hate you," he muttered, without any actual hatred in his voice. Rather, there was the hint of laughter, fond amusement, something that made Harrison's heart twist in a painful way he did not care to analyse.

"Oh, I assure you, Barry, the feeling is mutual." He couldn't help the smile that broke out on his face, though, no matter how hard he bit the inside of his lips to suppress it.

**Notes for the Chapter:**

> If anyone has better information on Barry's caloric needs or those protein bars, that'd be great. I did my research, found nothing concrete, and ended up just doing maths based on the whole 850 tacos (sans cheese and guac) thing.
> 
> 23/01/16: Made a slight edit after research for further parts of this series revealed I made a glaring timeline error.


	2. Rate of Reaction

The problem with Velocity-6 wasn't that it didn't _work._ It worked exceedingly well. Although Harrison would have preferred that the test had not involved removing a bullet from his chest, he was willing to concede that such a situation was probably the only way to convince Jay Garrick to be a guinea pig.

More the pity, because he hadn't been in any shape to observe whether it was that the drug had -albeit temporarily- restored Garrick's speed, or if Garrick had in fact regained his speed and merely was choosing to not use it. Caitlin held fast to the former hypothesis. It had its merits. After all, the others had observed that even when Barry's speed had been stolen from him, his cells still retained the potential for it, the physiological changes that allowed him to actually use his abilities. So it did make a level of sense that, if Garrick's cells were the same, just lacking in some sort of 'spark', that Velocity-6 had provided fuel for them.

That said, there was a large part of him that uncharitably believed Garrick _had_ regained his speed, but was hiding like a coward. Not that Garrick had ever had the capability to vibrate _through_ objects in all the observations of his abilities that Harrison had made back home, observations pieced together through witness statements and official reports, the rare film of his fights. Except the point of Velocity-6 was to enhance speed, so it made sense, then, that if Garrick had his powers back, then it enabled him to do what had been previously impossible for him.

No, it wasn't that version six hadn't worked. It worked like a charm. The problem was, it didn't _last._ By all accounts, Jay had barely enough time to extract the bullet before his speed left him once more.

Harrison was a perfectly rational level of relieved that Garrick hadn't burned through the drug even a second faster. Having a hand merged into his chest sounded not only intensely painful, but also quite fatal. Though who knew for certain what might happen if someone failed at phasing through a solid object.

Well, purportedly there had been one man who might have known the answer, but Harrison didn't care to think about him, and it hardly mattered anyways, considering the man had suffered a fatal exception error in regards to his existence.

He rested his face against his hand as he leaned against the desk. Stared at the monitor in front of him. Biochemistry was definitely not his strong suit. He knew Caitlin would be in at some point today, but he didn't want to rely entirely on anyone else for this. Not when he had an end goal in mind that would require the utmost secrecy. He had to perfect the speed enhancing formula, had to make sure that when it worked, it would hit hard and fast, and then _last._ It would be the backbone of the final iteration of Velocity, a necessary component to ensure immediate effect.

But first, he needed to figure out a viable alternative for sodium chlorate, one that the body wouldn't burn through so quickly.

Harrison drummed his fingers against the desk. The _stupid_ answer was a higher concentration of sodium chlorate. Essentially, more fuel. He actually was ashamed of himself for even thinking of that. It was a common bugbear in certain branches of physics; the need for more power countered by the fact that one had to transport the source of the fuel for that power with them. No engineer worth his salt would have ever simply gone to 'carry more fuel' as a potential solution.

He was going to blame tiredness, even though he'd been sleeping much better since the 25th.

His thoughts were interrupted by a voice cutting in.

"Hey Harry, working hard or hardly working?"

Harrison turned just enough in his seat to see Cisco approach the desk, a plastic shopping bag in one hand. He quirked an eyebrow at the younger man.

"Yes," he replied.

Cisco dug into the bag and held up an obscenely _neon_ can. He wasn't entirely sure that hue of yellow was meant to be anywhere _near_ that obnoxious an aqua. He'd have settled for knowing that both colours were allowed to exist in the same universe, although he'd have preferred a universe without either.

"Want one?" Cisco offered.

"…I'm somewhat afraid to ask what it _is_."

Cisco grinned and set the can down on the desk so Harrison could read the label. Or attempt to, at any rate, if he had any desire to risk a migraine by staring too long at the can. "New energy drink! It has fifty milligrams of caffeine per ounce. _Fifty._ Do you know what an advancement in energy drink technology this is?"

He eyed the neon abomination skeptically. "You say 'advancement in energy drink technology', yet all I hear is 'advancement in increasing the rates of cardiac arrest'."

"…Way to be a downer, Harry. Way to be a downer."

The barest hint of a smile threatened to break out, so he twisted his mouth to try to stop it. "I live to serve."

Cisco plopped down in the seat next to him and pulled out another can, this one in an only mildly less eye-searing royal blue and fuchsia. He popped it open and took a sip as he studied what was on the monitor in front of Harrison. "Velocity seven?" he asked.

"Yes," Harrison turned back to the computer as he spoke. "Velocity six was a success, but not a perfect one. It has no lasting power."

Cisco opened his mouth, but Harrison cut him off. "And I am well aware that is what she said."

He enjoyed the gaping stare he got as Cisco floundered for words.

"Okay, no. You are not allowed to make jokes like that. Not allowed, do you hear me?!"

Harrison chuckled softly. "Whatever you say, Ramen."

"…You do that on _purpose,_ don't you," Cisco grumbled.

He just raised his eyebrows briefly in response.

"Okay, fine. Whatever. So obviously the solution is not to just make it more concentrated or up the dosage, because that is a stupid solution. And while we _could_ just make a glorified insulin pump, except for speed drugs, that is also a stupid solution. Which leads to the question of, why are you even working on this when you know Jay isn't gonna let you test it on him?" Cisco gestured pointedly with the hand that held his drink.

"Who said I was going to ask _Garrick?_ " Harrison countered mildly.

"You are _not_ using Barry as a lab rat."

"That's up to him, now isn't it."

Cisco sighed in a manner Harrison would have thought exaggerated from just about anyone else.

"I don't suppose you know anything about biochemistry?" Harrison asked.

"No-ot really," Cisco confessed. He took another drink before he continued. "I mean, if you want a thing built, I am definitely your - best bet. I can totally build things. But there's a reason the energy bars have been a joint effort between me and Cait, and it's not that I don't have time to work on them by myself."

He leaned back in his seat and turned towards Cisco fully, crossed his arms over his chest. It sounded like Cisco had been about to say something other than 'best bet', but he decided to ignore that in favour of a more productive line of conversation. 

"The challenge of packing 30 000 bio-available calories into a modestly sized package."

"Bingo. And then you've got the challenge of making it something Barry is willing to eat on a regular basis."

Harrison tilted his head as he considered that. Then he reached for the yellow can and opened it. It smelled distressingly of artificial banana. Which was a slightly better alternative to the lemon he had been anticipating. "Why not make them less calorically dense?"

"…Less calorically dense? Are you kidding me? The idea is to make something so he doesn't go broke on regular food."

Harrison rolled his eyes. "In which case, you're failing miserably, unless he was lying to me about not eating them for every, or even most meals."

Which, admittedly, was a lie. Barry had never explicitly stated that; he'd merely mentioned that he had no desire to eat one for every meal.

Cisco huffed and slouched in his seat. If that grumpy Siamese that was so popular on the internet became a person, in that moment Harrison would have completely believed that person was Cisco Ramon. "It's a work in progress."

"If you make them even just 15 000 calories, you'd probably have room for actual flavour molecules," he pointed out. And then he finally bit the bullet and took a sip of the drink. Oh _God,_ the taste alone was awful enough to wake him up without the caffeine. Although, given the main component of the flavour… Harrison winced, then held up the can. "Take this for example. It tastes _overwhelmingly_ of caffeine. It's _terrible._ I would only finish this if I were exhausted and had no other way to wake myself up and were in a situation where sleeping would be potentially fatal."

Cisco glanced down at his own can. "…Okay, yeah, I'll agree with you there."

"So, the answer would be _less_ caffeine if you wanted to improve the taste."

"But if we reduce the caloric density-"

"Then he has to eat more of them. Heaven forbid." Harrison's tone was dry enough that it rivalled the Sahara.

"…Okay, you might have a point," Cisco finally conceded. "I mean, I've seen how much pizza he can put away. I have no idea how he does it. Does he just digest it all immediately?"

Harrison thought about the mechanics of that, and then shuddered. "I have no idea, and I also honestly don't want to have an idea."

Cisco looked pensive as well, and then he cringed. His entire body cringed. "Yeah. Yeah, I don't wanna think about that either. Wow. I need a drink now. And _not_ the caffeinated kind."

He nodded in agreement, then raised the can to his lips once more. It was awful, yes, but it gave him something _else_ to think about beyond speedster digestive processes. Then he sat his drink down and turned back to his work. Well, at least today wasn't entirely wasted, if he'd at least managed to help solve the problem of making meal replacement bars that Barry would eat. Though it did nothing to help him with Velocity-7.

Harrison sighed. He pinched the bridge of his nose, which nudged his glasses up.

"…This goes against everything I hold dear, but why not make it _less_ effective?"

He looked over at Cisco, brows furrowed as he considered his words. "Less effective."

"Yeah. If the problem is that the body burns through it too quickly, then maybe there's something that can slow down how fast it's burned? I know, I know, usually you wanna make a _more_ efficient fuel, but in this case it would be more efficient if you could get a longer effect for the same dosage."

He considered that. Ran it through his head. And then mentally berated himself because _why_ was everyone _else_ thinking of things _he_ should have thought of _first?_

"I'm right, aren't I?"

He didn't even have to look at Cisco to know there was a positively shit-eating grin on his face. Harrison took his glasses off and rubbed his hand over his eyes, grumbled under his breath. "I admit I had not considered that angle."

"Booyah! Who just outsmarted the smartest man alive? This guy!"

He peered through his fingers to see that Cisco had leapt from his seat, arms held up triumphantly. He looked half-ready to begin some kind of ridiculous victory dance, which absolutely was not going to stand.

"If you do not shut up right now, Crisco…"

Not even that fazed him, because Cisco just continued grinning blindingly and _bowed_ to him. "Thank you, thank you, I'll be here all week."

Harrison groaned and closed his eyes again. "Could you maybe _stop_ crowing and suggest _how_ I reduce the rate of metabolisation, if you're so clever? I'm a physicist, not a doctor. Actually, I _am_ a doctor, but not that _kind_ of doctor. I have a doctorate; it's not the same thing."

That worked surprisingly well, because Cisco looked like he was about to continue, until he actually thought about what Harrison had said. Then he got an utterly shocked look. "…You did not."

"Didn't what?"

"That movie actually exists on Earth-2?!"

"What movie?"

"…Never mind," Cisco frowned, and sat back down in his seat. "But I definitely know what we're watching next team movie night."

"Focus, Ramon."

Cisco sighed. "Fine, fine. But I can't really help you beyond that. Biochemistry is really closer to Caitlin's thing. Like I said, I just build cool gadgets."

Which was true enough.

Harrison nodded once. He saved his work, then, even though he was certain he'd be deleting most -if not all- of it once he consulted with Caitlin. And read up some more on metabolic processes. (Read a _lot_ on metabolic processes, if he was honest. For a moment, he desperately missed Tess, because her insight would have been equally invaluable.)

"Guess you don't need me anymore," Cisco muttered.

Harrison tapped a finger pensively against the top of the mouse. " _Actually..._ "

**Notes for the Chapter:**

> I hear some of you saying, "But Blue, rate of reaction is a _chemistry_ term, not a physics term!"
> 
>  
> 
> [I refer you to this relevant XKCD.](https://xkcd.com/435/)


	3. String Theory

**Notes for the Chapter:**

> [Exposition ahoy.](https://www.youtube.com/watch?v=7jz7rFuZZZc)

"Quit looking at me like that," Harrison huffed.

He'd sat back in his chair, swivelled it to face Cisco once more. Which had only led to his current state of annoyance, because Cisco was looking at him like he had absolutely lost his mind.

Truth be told, he wasn't entirely certain he _hadn't,_ that all of his decisions of late had not been the result of some stress-induced mental break. He'd always been told that he'd crack if he wasn't careful, didn't manage his workload better. Take that tendency to work past the physical limits of his body, add in the psychological stress of worrying about Jesse's safety whilst trying to outsmart a man(?) who always seemed to be one step ahead, and throw in a handful of _feelings_ (which were distinct from emotions in that he wasn't quite sure what they were and he did not want to analyse them in any way, but he was well aware he hadn't experienced anything like them in at least a decade); and quite honestly he was surprised he hadn't broken down _sooner._

And Cisco was still looking at him like that.

"…You know, I thought our Dr Wells was maybe a little crazy, but I think you just _definitely_ beat him in that department," Cisco said, at last.

Would the comparisons to his false counterpart _ever_ cease? He rolled his eyes. "I fail to see how wanting to work with you on marksmanship makes me _insane._ "

"How about the fact that I'm not the superhero here? Why do I need to know how to shoot when _Barry_ is the guy who fights the criminals?" Cisco gesticulated wildly as he spoke.

"How much experience do you have with rifles?" He knew the question was a slight non-sequitur, but he _was_ going somewhere with it.

"Rude. You don't answer questions with more questions; that's not how this works!" Cisco scowled petulantly. "But the answer is pretty much none. Like, enough that I can design some pretty neat guns, but that doesn't really require knowing how to use them beyond 'pull trigger, go boom'."

Pull trigger, go boom? Harrison's eyebrows inched slowly upwards at that one. Firearms of any sort were definitely more complex than that. "Mm. I have three decades of experience with firearms. Not just designing them or repairing them, but shooting. And yet, which of us managed to hit Zoom with the serum dart?"

Cisco fell silent at that.

"I had briefly considered that you were merely lucky, but then I considered the circumstances," Harrison continued. "In neither situation should Zoom have been aware of either of us shooting at him. Yet, when I shot, he turned and caught the dart. When you shot, it hit him."

"I was probably closer? Seriously, luck. It's a thing. Doesn't mean I need shooting lessons." Cisco shrugged. He still looked wary and nervous, however.

"You were closer, but at short distances it really doesn't matter all that much." He dismissed the notion entirely with a short shake of his head. "At least, not when all you need to do is hit the target. Which suggests to me that something else was in play."

"This is the part where you say it was my powers, isn't it," Cisco said flatly.

He pointed at Cisco, a slight grin stretched across his mouth. "Got it in one."

"Those just let me… see things. That have happened. Or are happening. With the potential of what could happen, but I haven't had any vibes like that so that's really still hypothetical at this point."

"Is that so," Harrison mumbled blandly. He let his gaze slip away, to look at -past, really- the far wall. He brought his ankle up and rested it on his knee, reached over and took up his energy drink once more. The more he sipped, the more he regretted his life choices, but he was simultaneously thirsty and… not necessarily lazy, but disinclined to find something else to drink. "You call them 'vibes'. Why?"

"Uhhh… mostly 'cause it's slang, you know? 'Oh, I'm getting some bad vibes off this guy.' That kind of thing. I mean, I really have no idea how these powers work. I don't think any of us do." Cisco shrugged, palms up towards the ceiling.

"I have a hypothesis."

"Most people would say they have a theory, y'know."

"And that would be why there is a not insignificant number of people who think that evolution is unproven; now focus," Harrison snapped. "You're familiar with string theory. I believe your powers work somewhat along those lines."

Cisco gave him a puzzled look as he thought about that. "So, what you're saying is that… somehow I can see across different 'strings' into other places and times? Is that what you're getting at? Because otherwise I don-"

"That's exactly what I'm saying. If we follow the supposition that strings exist in other dimensions than the ones we experience, yet still interact with ours in observable ways -as the elementary particles-, then it stands to reason that they intersect with our dimensions in multiple points."

"I can kinda see how you'd come to that conclusion since time interacts with the rest of our world differently depending on reference frame, but I'm still not quite following your crazy logic."

Harrison thumped the back of his head lightly against the backrest of his chair. "How do I… Ah."

He hopped up out of his seat and darted into the next room. A few seconds later, he returned, carrying two sheets of paper and a pencil. "Allow me to explain."

"Go ahead, I'm all ears." Cisco gestured with his right hand, a slightly swirling motion that reinforced his words.

Harrison grinned, and then set one of the pieces of paper down. Cisco leaned over like he was expecting him to start writing his explanation, or perhaps draw a diagram. That was not his intention at all, however.

The sharp snap of his pencil tearing through the paper he still held made Cisco jump half out of his seat.

"Holy Hannah!" he yelped. His wide-eyed stare was fixed on the sheet of paper in Harrison's hand, with the pencil stabbed halfway through it.

"The paper is our current position in spacetime. The pencil is a string. Could be any string; we could call it a tachyon if you'd like, but it's honestly unimportant. What is important is that the string is an open string, which means it has to be connected at the ends to a brane. For purposes of this example, we'll assume that the string connects two separate branes, although given that branes need not line up entirely with our perceived dimensions, it's not impossible that the string never leaves the brane."

Harrison picked up the second piece of paper then. "Our starting brane aligns with the position in spacetime we presently exist in. The ending brane aligns with a different position in spacetime, represented by this sheet of paper."

This time, Cisco was prepared, so he didn't jump when Harrison stabbed the pencil through the second paper.

"Our string connects the two branes. And your powers allow your consciousness to follow that string to observe the other point in spacetime."

"Which has what to do with me hitting Zoom with the speed-dampener? Oh, right, nothing, unless you're somehow saying I, I dunno, saw where to aim?"

Harrison shot him a flat look. He dropped his model on the desk and turned away. It physically pained him to hold in the comments he wanted to make on Cisco's relative intelligence right now, but he managed it. If only because he needed the boy to _listen,_ not return to his prior conclusion that Harrison Wells Was Not To Be Trusted.

"Strings correspond to elementary particles. Particles can be interacted with. If you can _perceive_ the strings, then you can _interact_ with the strings."

Cisco exhaled slowly, realisation bright in his eyes. "So, what you're saying is that somehow I _made_ the dart hit him."

"Or made it so he was not aware of or able to react to it," Harrison added. "Either way, if you will permit me to work with you on marksmanship, we will be able to figure out how, exactly, your powers influenced the outcome."

Cisco frowned as he thought about that. He looked down at his hands. Looked up. Over to the entry to the Cortex. Down. Back up at Harry. Sighed. "Okay. When do we start?"

* * *

"Ow!"

Harrison refused to dignify that exaggerated yelp with even a snort. Instead, he lightly kicked Cisco's elbow again, in the vain hope that the boy would _take the hint_ and move it in a bit closer to his body like he'd been _told_.

As if on cue, the door to his makeshift shooting range opened, and there Barry stood, with Caitlin and Joe behind him. It appeared they'd found the note he left for them. Barry looked more than a little confused… and there went the past five minutes of work, as Cisco hopped to his feet and-

Oh no he did _not._

"Barry! I am _so_ gla-AHH! What the Hell, Harry?!" Cisco's relieved cry turned sharply into a slightly pained yelp when Harrison grabbed him harshly by the shoulder and dug his fingers down behind his collarbone.

"If you _ever_ **drop** my rifle again, we will have problems, Cisco. Are we clear?" Harrison growled. He reinforced his point by pushing down slightly with his hand.

Cisco flailed at him, but it was useless, and not because Harrison was holding him too firmly but because Harrison was being pinned against the wall by Barry. He winced, shoulder blades sore from where they'd struck. And not at all because Barry was giving him a disappointed, reproachful look. Harrison sighed.

"Okay, that was perhaps uncalled for," he conceded. Which was the closest he was giving to an apology without being forced into it.

"Perhaps? Perhaps?!" Cisco yelled, waving Joe off. "That _hurt!_ "

"That was the point," Harrison mumbled.

"You know, you're really not helping me like you any," Joe pointed out. "If you're so smart, I'm sure you can figure out how to repair your rifle if Cisco accidentally damages it."

"It's not a matter of _if_ I can fix it, it's a matter of _him respecting my property,_ " Harrison snapped. "Besides, it's not like Thawne kept a stock of rifle parts around, so _someone_ would have to get the parts for me."

Barry sighed and let him go. Harrison practically bolted to scoop up the M16 and look it over, check to make sure nothing had been damaged by the -admittedly short- drop. He missed the puzzled frowns from everyone.

"Where did you get that?" Caitlin asked.

"Hm?"

"We don't keep assault rifles around. We don't keep _any_ rifles around, actually, except the other two you brought here. But that's not your dart gun and that's also not your… I don't even know what you call it," she explained.

"B.F.G." he muttered as he checked the alignment of the sights. He glanced over at Joe, then, as he considered the actual question that Caitlin had asked. "And I believe I will exercise my fifth amendment rights at this moment."

"You _stole_ it?!" Joe yelled.

"Pleading the fifth!"

**Notes for the Chapter:**

> I am still not a physicist.


	4. Interlude: Five Rules of Gun Safety, as told by Cisco Ramon

**Notes for the Chapter:**

> Interlude chapters will be extra bits related to the main story from the perspective of characters other than Harry. Saves me having to make a separate story and alla youse from having to hunt the story down and figure out where it fits into this one.
> 
> Interludes will also not always fit into the theme of science! because, well, at least in this case there isn't a whole lot of science! I can fit into the theme of gun safety. So why force it?
> 
> We're starting with the continuation of Cisco's adventures in marksmanship, because does anyone seriously think that Cisco wouldn't get the Gun Safety Talk from both Joe AND Harry?
> 
> Yeah, didn't think so.

"Hey, Cisco, are you okay?" Joe asked as he caught up to the younger man in the hallway.

Cisco paused, because he kind of had to think about it? On the one hand, his shoulder was still a bit achy from where Harry had grabbed it -the man had bony fingers, and he was _so_ remembering that whole dig behind the collarbone trick-, but on the other… It wasn't that big a deal. Yeah, it hurt, but it wasn't as if Harry had shoved his hand at his chest _again,_ and that had been a lot more traumatising mentally.

"Yeah," he said, at last.

Joe frowned at him. "Are you sure? He didn't have to grab you like that."

"No. I mean, yes. Yes, I am sure. No, he didn't, but I guess he had a point about how I shouldn't treat his stuff like that."

Joe snorted and looked away. His hands came to a rest on his hips. "I don't think you can call a stolen rifle his, but considering I've kind of been ignoring the fact that he hasn't returned that Mercury Labs prototype, I guess I'm gonna have to let this one slide too."

"…Wait, he stole that energy gun from _Mercury?_ Geez…" Cisco ran his hand through his hair with a laugh, "I bet Dr McGee is pissed. I'm surprised she hasn't bolted everything to the floor, including the _staff._ "

That made Joe chuckle. "She's still calling me for updates. I haven't quite convinced her it _wasn't_ Harrison Wells she saw taking it."

"I could look up some studies about how bad human memory is?" Cisco offered.

"I think she's aware of that, Cisco, but it's tempting." Joe sighed. "Anyways, I wanted to talk to you real quick, and not about Wells."

"I'm all ears. Lay it on me," Cisco said as he held his arms out. He figured whatever it was was probably work related. Or maybe some information pertinent to the whole Team Flash business they had going.

"Don't let me _ever_ , and I mean ever, hear about you dropping a gun again." Joe stared at him, expression deathly serious. "I'm guessing Wells knew you didn't have much experience, so the gun wasn't loaded? But that doesn't change the fact that you could have seriously hurt someone if that thing went off."

Cisco gulped. He hadn't even thought about that. And, yeah, he'd appreciated the back-up when Harry had grabbed him, appreciated that Joe hadn't laid into him in front of everyone. But he hadn't thought about the fact that the rifle he'd been holding had been designed to work by a percussive force setting off a small charge in the bullet. And it didn't matter if the bolt was set off by him pulling the trigger or by a sharp impact. "…I'm sorry. I didn't… I wasn't thinking. I won't do it again. And not just because I think between you and Harry there wouldn't be much left of me to bury."

"Relax, I'm not going to kill you for a simple mistake. I just want you to think about safety. You'd feel terrible if someone innocent got hurt because of an accidental discharge." Joe offered him a slight, reassuring smile. "That said, if Wells gives you a hard time, come get me. Actually… if you can explain why he wants you to learn how to shoot, I could teach you."

"Oh! He thinks that somehow my powers made it so that I hit Zoom with the dart," Cisco explained. "So he wanted to find out if that was the case, and if it _was,_ then _how._ "

"Huh," Joe nodded. "Sounds reasonable. But you don't need him around for that." 

"Yeah, well… We'll see, okay? If I work with him on this, it's more time he spends not off by himself being shady, you know?" Cisco shrugged and offered a slight grin.

Though… honestly, a month ago, he would have grudgingly worked with Harry on this _solely_ to keep an eye on the guy. Now, he wasn't so sure. When he wasn't being an absolute _dick,_ he wasn't all that bad to be around. Aside from the moments when Cisco forgot and mistook him for the Reverse Flash. But there had definitely been a bonding moment over blowing up his poor drone, even if he still wasn't quite sure he followed Harry's explanation of what he'd done to make all the bombs go into the breach. And the guy was _totally_ quoting movies at him, even if he refused to admit it.

Say what you will, it was hard to absolutely _despise_ a guy who quoted _Treasure Planet._

"Alright," Joe said. "But like I said, if he gives you a hard time, tell me."

"You'll be the first to know," Cisco promised. He shoved his hands in his pockets, and felt a little bad about crossing his fingers.

* * *

The next day when he rolled into the lab, there was no sign of Harry in the Cortex. So he went down to his workroom, because the guy had absolutely commandeered it in spite of his protests. There was a _cot_ in there and everything. Of all the workspaces in this building…

Well, this one was empty too.

Crap. Where was he?

He got his answer just then when something thwacked him on the head. Cisco yelped and spun around to see Harry standing there, holding a small stack of papers in his hand.

"Morning," he said.

"Dude, not cool," Cisco groused. He rubbed his head where the papers had struck. Not that it _hurt,_ but it was the principle of the matter.

Harry didn't even acknowledge that, which actually did not bother him in the least because he was so not prepared to deal with the level of snark that man could dish out. Seriously, he'd swear that Harry had gotten a doctorate in sarcasm.

Instead, he just held the papers out to Cisco. Naturally, Cisco took them from him, because he was curious, and he was also not a cat so it wasn't like it would kill him. He flipped through the pages and… wait, why did these look like print-outs from a military manual?

"Today's lesson: gun safety. We're gonna work from that since I doubt anyone would appreciate a more practical demonstration on how dangerous firearms can be."

Harry sounded almost bored as he said that, his voice was so dry, but Cisco noticed the way he rubbed the left side of his chest when he thought Cisco wasn't looking. He winced, because… yeah, Harry definitely had way more practical experience with being shot than anyone ought to. No wonder he'd been so pissed off yesterday; it probably hadn't been about the potential damage to the rifle at all.

"Sounds good. Joe mentioned a few things to me yesterday after we left, but… in depth is good. In depth is totally good."

That earned him a soft huff. "Yes, in depth is very good. Honestly, I should have done this before even putting the damn thing in your hands. But…"

Oh no, he wanted to hear what followed that 'but'. "But…?"

"…It's not important," Harry looked away.

"Yes it is."

"No, it isn't."

"Is too!"

" _Frisco._ "

He pouted, because why not? It worked sometimes, the whole kicked puppy thing. "Come on, you had to have had a good reason for just jumping right into the practical stuff!"

Harry rolled his eyes and sighed. "Yes, of course I did."

"So, out with it!"

"No."

Which made him think Harry actually _hadn't_ had a good reason. Because if it had been because he'd thought Cisco was at least familiar with basic safety because he'd built weapons before, then he'd have admitted that by now. Which meant… Oh _man,_ he was _never_ gonna let Harry live this down if he was right.

"You got over-excited."

That made the man tense, but he looked at Cisco with a blank expression. A _too_ blank expression. "The only thing that could possibly excite me at this point in my life is you putting a bullet between Zoom's eyes."

"…Okay, not sure I could do that. You know, the whole killing a guy thing? Even if he is evil. But maybe we can figure out how to use my powers so _you_ could?"

Harry hummed consideringly. "The idea has merit. But first, gun safety. So we can at least ensure you can hit him with an improved power dampening serum."

"C'mon, let's sit." Cisco headed into his workroom and plopped down in the chair.

Harry followed behind him, and leaned against one of the tables. "We'll start with the most important rule of gun control-"

"Hit the target?" he cut in cheekily.

It was so worth the glare he got, because there was no ice in Harry's gaze. Actually, if he didn't know better -wasn't reading too much of Dr Wells into Harry's expressions- he was pretty sure Harry was trying his hardest to not laugh.

Cisco grinned triumphantly when Harry's shoulders began to shake, and he ducked his head. There it was.

"I… yes, hitting the target is very important," Harry finally said, amusement thick in his voice. "But that's not one of the rules."

"Damn. I bet the rules are all about what I _can't_ shoot." Hey, he had the guy in a good mood already, so it just made sense to keep joking.

"Not quite," Harry corrected. He looked up, finally, the corners of his mouth tugged up in a way that suggested he was suppressing his smile. "They're more along the lines of how to not shoot something you don't want to shoot."

"Ooooh, like I shouldn't point a gun at something I don't want to shoot?"

"That would be rule number two, yes," Harry agreed.

Cisco frowned, then thought about it. He resisted the urge to consult the papers in his hand. There wasn't anything _wrong_ with researching the answer, but he wanted to see if he could figure these out on his own. After a moment he gave up and glanced down at the page he'd flipped to earlier. "Keep your finger off the trigger until you're ready to fire? Huh? That's not how it works in the movies."

"That would be because Hollywood is terrible at portraying anything with an acceptable degree of accuracy," Harry said. "But, yes, that is rule three. Otherwise, something could startle you, and… well, then you have holes in places that shouldn't have holes."

Cisco winced and laughed, because wow that sounded painful but the way he _phrased_ it.

"Rule four is to keep your weapon on safe until you're ready to shoot. Helps prevent negligent discharge," Harry explained. He tilted his head and glanced off to the side, over to where he'd left his weapons. "Rule one, however, is the most important. Always. _Always._ Assume it's loaded."

"Wait, what? But, yesterday. You unloaded it. And did that whole thing where you pointed it at the ceiling and pulled the bolt back and looked inside it." Cisco was really confused. In fact, Harry had even said he was making sure it wasn't loaded before he handed it over, because he didn't want to work with a loaded rifle just yet.

"Yes, I did clear it. And I'm going to show you how to do that during our next practical session. But… if you treat every gun like it's loaded, then you're never going to do anything _stupid_ if you happen to find a firearm sitting out. Again, the entire point of these rules is to make sure you only shoot when and what you intend to shoot."

"Riiiight," Cisco nodded. Okay, that made sense. That all made sense. "So I'm guessing rule five is don't drop the rifle, dumbass, because it could go off and who knows where the bullet will end up?"

Harry openly laughed at that. Well, okay, it was one of those laughs that was more like a rhythmic exhale, but Cisco was totally going to take it. "Yes. Like I said, if you _ever_ do that again, we'll have problems."

"…Do I want to know what kind of problems?"

"I was considering a demonstration of what being shot feels like, but I think Detective West would decide I needed a reminder of that myself if I did so." Harry shrugged, appearing totally unfazed by the idea of being shot again.

Which Cisco doubted was actually the case, just based on how Harry had acted earlier. If it _was,_ though? He was just gonna declare Harry to be the stone-cold badass of the year. Actually, he was in the running just for looking entirely unbothered by the idea of being used for target practise.

"Yeahhhh he kind of said as much yesterday, actually. I think he'd prefer it if he was the one showing me how to shoot," Cisco admitted.

"Hm," Harry eyed him. "So why isn't he?"

"Huh?"

"Why isn't he teaching you, then? I can't imagine you actually _want_ to spend time with me." Harry crossed his arms and straightened up off the edge of the table.

Cisco wasn't sure he was ready to admit that he kind of _did_ actually want to spend time around Harry, because the guy was an ass and there were still too many moments that made him think of Eobard Thawne, so he just shrugged. "Don't wanna bug him. He's got a lot on his plate with the metahuman task force and all. You, on the other hand… No offense, but you have a lot of time on your hands. I refuse to believe you spend all day, erry day actually _working_ on things to stop Zoom and rescue Jesse. And thinking about it? So does not count."

That answer seemed satisfactory to Harry -which was good, because there was no way Cisco could bullshit his way out of the honest answer otherwise-, because he nodded in that kind of thoughtful way people did when something made sense to them. "Fair enough. Wanna try more practical or should I go over that packet with you point by point?"

"…Uh. Shouldn't we do more of the…" Cisco shook the papers so they made a slight flopping noise, "before I pick that thing up again?"

"There's really not a lot to safe handling. If you can't remember those five rules, then I question why my counterpart hired you."

"…Fair enough." Though it then raised the question of why did Harry even bother asking if he wanted to go through the packet. He'd have to read it on his own time, though, because he would not put it past Harry to have a pop quiz on the contents at some point.

"So. Practical?"

He _swore_ Harry bounced slightly on the balls of his feet when he said that. Cisco narrowed his eyes suspiciously. Right. Nothing could get Harry excited except Zoom's death his _ass._ "Yeah, sure."

"Excellent," Harry turned and headed over to where he'd propped his rifles up. He grabbed the M16 and held it up, checking the chamber, before he turned back to Cisco. He held it out, one-handed, by the handguard. "Say hello to my little friend."

"They have _Scarface_ on Earth-2? Why does this surprise me?" Cisco said in disbelief as he took the rifle.

"Actually, no, we don't."

Cisco stared at him as he tried to process that. "But. When did you? _Why_ did you?"

"Because I needed something to do while waiting for some code to compile? I _am_ human, shocking as that may be," Harry sniped.


End file.
